There is considerable interest in photonic integrated circuit technologies for both active and passive devices.
It is well known to transport electronic data between a data source and a data destination over an optical data path. The use of fiber-optic communications lines presents one well-known example of an optical data path. Indeed, with the continued development of optical communications technologies, functions previously performed in the electrical domain are now migrating into the optical domain. Optical channels are now replacing electric wires for the communication of electronic data, and optical signal processing is now replacing transistor signal processing for the manipulation of electronic data.
This migration towards optical solutions has even progressed down to the level of the integrated circuit. In this regard, the prior art teaches a number of optical waveguide structures implemented in semiconductor substrates. Compact on-chip optical waveguide structures are recognized to have extensive uses in semiconductor photonics.
As semiconductor integrated circuit process technology shrinks towards nano-scale features it is important for the optical waveguide structures formed in or supported by the integrated circuit substrate to also achieve nano-scale dimensions. However, it is difficult to make well-defined on-chip optical waveguide structures, especially in the nano-scale. In particular, there is a need to form densely populated hollow optical waveguides.